Why do windmills typically have 4 blades, yet all modern wind turbines have 3?
In: 9124
Ok I used to work at Vestas, I worked both in attaching and testing the ring gear motors that rotated the unit, as well as I worked in finishing for blades. The blades are heavy, very heavy, some models have blades that weigh 35 tons. Most of the weight is in the mounting rig however. To finish the blades it takes about 7 employees 10 hours of sanding with hand held power sanders. The finish material is epoxy and fiberglass composite sandwiching a foam center with a more dense microballoon and epoxy spar in the center bringing the load bearing aspect to the blade. however some of the new new models proposed for future will use carbon fiber blades once a manufacturing process that doesn’t cost above $10 million or so is reached.
Each blade in itself is a costly process not just to build but to also install. The highest paid in the company outside of the execs, so specifically blue collar employees at Vestas, are the field installers. These fellas are driving a specialized truck that has both a driver in the front and the back, they have an insane crane that costs hundreds of dollars an hour just to pay the operator, not including any logistical costs (which could probably be in the hundreds of thousands of dollars per blade, installation logistics only). Each blade is already a massive undertaking requiring finish sanding by 7 decently paid employees for 4-6 hours, that’s not including the cure time beforehand for the materials as they get out the specialized vacuum chamber oven.
This is a massive undertaking and taking away 1 blade from a 4 blade design gives you 10 completed wind turbines if you have 30 blades, which is actually can at times be the main production bottleneck as well. It’s arguably easy compared to just assembling a bunch of gearboxes and plugging in some generators, testing process is simple too with designed software that can completely test the unit from 1 IO socket.
So imagine you own a wind turbine company, your not going to keep a lead engineer that tries to talk you into building less wind turbines for more money. Maybe you could build 4 blade turbines with 16 blades and end up with 4, but is it really worth it? Why not just build 5 and have another blade left over to use as a replacement in the event one of the units off lines due to blade related fault?
And 2 blades just isn’t enough, you get more power from 4x of 3 blade units than you do from 6x of 2 blade units per dollar spent. Wind turbines are actually sold to customers by power generation, in megawatts, so power generation per dollar is the name of the game. Get as much as you can out of each nacelle, but don’t spend too much money on blades when you reach the point of not gaining enough to rationalize doing so
Why do windmills typically have 4 blades, yet all modern wind turbines have 3?
In: 9124
Ok I used to work at Vestas, I worked both in attaching and testing the ring gear motors that rotated the unit, as well as I worked in finishing for blades. The blades are heavy, very heavy, some models have blades that weigh 35 tons. Most of the weight is in the mounting rig however. To finish the blades it takes about 7 employees 10 hours of sanding with hand held power sanders. The finish material is epoxy and fiberglass composite sandwiching a foam center with a more dense microballoon and epoxy spar in the center bringing the load bearing aspect to the blade. however some of the new new models proposed for future will use carbon fiber blades once a manufacturing process that doesn’t cost above $10 million or so is reached.
Each blade in itself is a costly process not just to build but to also install. The highest paid in the company outside of the execs, so specifically blue collar employees at Vestas, are the field installers. These fellas are driving a specialized truck that has both a driver in the front and the back, they have an insane crane that costs hundreds of dollars an hour just to pay the operator, not including any logistical costs (which could probably be in the hundreds of thousands of dollars per blade, installation logistics only). Each blade is already a massive undertaking requiring finish sanding by 7 decently paid employees for 4-6 hours, that’s not including the cure time beforehand for the materials as they get out the specialized vacuum chamber oven.
This is a massive undertaking and taking away 1 blade from a 4 blade design gives you 10 completed wind turbines if you have 30 blades, which is actually can at times be the main production bottleneck as well. It’s arguably easy compared to just assembling a bunch of gearboxes and plugging in some generators, testing process is simple too with designed software that can completely test the unit from 1 IO socket.
So imagine you own a wind turbine company, your not going to keep a lead engineer that tries to talk you into building less wind turbines for more money. Maybe you could build 4 blade turbines with 16 blades and end up with 4, but is it really worth it? Why not just build 5 and have another blade left over to use as a replacement in the event one of the units off lines due to blade related fault?
And 2 blades just isn’t enough, you get more power from 4x of 3 blade units than you do from 6x of 2 blade units per dollar spent. Wind turbines are actually sold to customers by power generation, in megawatts, so power generation per dollar is the name of the game. Get as much as you can out of each nacelle, but don’t spend too much money on blades when you reach the point of not gaining enough to rationalize doing so
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